Airbag systems have been widely adopted in recent years for improving the safety of riders in automobiles. In these systems, a gas generator is operated by signals from a sensor detecting a collision and inflates an airbag between a rider and the body of the automobile. The gas generator is required to produce a sufficient amount of gas to inflate the airbag in a very short time.
The compositions used to generate gas in current gas generators contain an oxidizer and a fuel. The particular components used in a given composition, and the amount of these components, greatly affects the properties (e.g., ignition rate, burn rate, etc.) and thus the suitability of a composition for inflating an airbag.
Gas generating compositions containing basic copper nitrate as the oxidizer and high amounts of guanidine nitrate as the fuel have been used for gas generation. In these compositions metal oxides and hydroxides are also used to improve combustion. Melamine is sometimes used as a secondary fuel and is thus present in smaller amounts than the primary fuel. While these materials are useful in many situations, improved compositions are still needed.
As an example, it is desirable to have a gas generating composition that has consistent performance over a wide range of pressures. Also, gas generating compositions that work well at lower pressures are also beneficial. The ability to work well at lower pressures can permit the composition to be used with lighter inflator structures, e.g., different inflator materials like aluminum or plastic may be used. Also, the inflator systems can omit booster chambers and filters if a lower pressure gas generating composition is used. Another likely advantage is that no separate auto-ignition material may be needed and there is a potential for direct ignition. Given these and other advantages, there is a need for new gas generating compositions with consistent performance over a wide range of pressures, and good performance a lower pressures. The compositions and methods disclosed herein address these and other needs.